in a single pill. Advil congestion relief. Thousands of people to search for the return of mr. Rabbit and a little girl's smile. Reporter: All of london on the hunt tonight for this lost bunny. Have you seen mr. Rabbit? Afraid not. Reporter: His name, mr. Rabbit, best friend of 3-year-old ruby stewart, inseparable since the day ruby was born. Here they are in paris sharing a hot drink together and with matching bandages on their forehead. Friday the stewards went out for dinner and the bunny vanished. I asked her where she thought he might be and she thinks the crocodiles eight him. Reporter: Zoe took to twitter using the hashtag find mr. Rabbit. There is people in japan, people in america, there is people in so, so many countries have helped. It's been amazing. It's been so lovely. Reporter: Volunteers are landing out fliers, missing, mr. Rabbit, age 3, with long, fluffy ears and no stuffing in his neck from being loved so much. We set out to retrace his steps. The stewards had dinner at the flat iron steak restaurant leaving around 6:30 p.M. They strolled around believing ruby was holding mr. Rabbit. Then they walked down busy oxford street and straight into this subway station. When they got home the bunny was gone. We asked everyone. If I do see it I will definitely get in contact with the people who have lost it. Reporter: No luck yet as a little girl waits to be reunited with her best friend. Mr. Rabbit, phone home. And we thank you for watching.

This transcript has been automatically generated and may not be 100% accurate.

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